'Khloe wasn't trying to get pregnant': Kim Kardashian admits her sister Khloe avoided having children because she knew marriage to Lamar Odom was in trouble

They appeared to have a fairytale marriage in every way apart from their trouble conceiving.

And Khloe Kardashian and Lamar Odom's efforts to have a child together were well documented with reports of IVF and visits to fertility specialists before their relationship fell apart in spectacular fashion last year amidst allegations he was taking drugs and cheating on her.

However, her sister Kim has now revealed Khloe not only avoided getting pregnant because she knew her marriage had problems, but even skipped appointments with fertility doctors behind her family's back.

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Knew you were trouble: Khloe Kardashian not only avoided getting pregnant because she knew her marriage to Lamar Odom had problems but even skipped appointments with fertility doctors behind her family's back

Speaking on Jimmy Kimmel Live on Thursday, Kim explained: 'Khloe wasn't trying to get pregnant.

'She wasn't showing up to these doctor appointments on purpose and behind our backs because she knew [the marriage] wasn't working.'

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Yet despite all of the allegations which have come to light about Lamar, Kim insisted: 'I always thought Khloe and Lamar would work out.'

And while Khloe, 29, ensured she did not have a baby with Lamar, Kim, 33, praised her younger sister as the best babysitter for her own daughter North.

Secret heartache: While Khloe and Lamar appeared deeply in love, her sister Kim has now revealed Khloe knew her marriage had deep problems

Kim and fiance Kanye West are currently living with her mother Kris Jenner and half-sisters Kendall and Kylie and although they all chip in with babysitting, there is no one she trusts more than Khloe with the tot.

When asked by Kimmel, who the best babysitter is, Kim replied: 'Khloe is definitely the best babysitter.'

And she had harsh words for her brother Rob, saying: 'Rob is the worst. I wanted him to spend time with her the last day and asked him to babysit for an hour.

End of the line: Khloe filed for divorce in December after months of turmoil with Lamar

'I pretended I had a meeting and he never showed up. Kourtney said it was the worse idea ever.'

Kim also spoke about her mother and stepfather Bruce Jenner's split last year, saying they are both much happier now that they are living apart.

'It wasn't a surprise,' she admitted. 'They have been living as friends for a long time. You want your parents to be happy. It was more awkward for them to live together and not sleep in the same room.

'I think it's the time away has gotten them back to that really good friend place and they realised they're better off as friends.'

'She lied to us!' Kim admitted even Khloe's family had no idea how bad things were in her marriage

Spilling the beans: Kim revealed Khloe's secret during her interview with Kimmel on Thursday